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BUG: KASAN: slab-use-after-free in v4l2_fh_open+0xc7/0x430
Read of size 8 at addr ffff888028490740 by task v4l_id/14232

CPU: 1 UID: 0 PID: 14232 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 v4l2_fh_open+0xc7/0x430
 em28xx_v4l2_open+0x157/0x9a0
 v4l2_open+0x20f/0x360
 chrdev_open+0x4cc/0x5e0
 do_dentry_open+0x953/0x13f0
 vfs_open+0x3b/0x340
 path_openat+0x2ee5/0x3830
 do_filp_open+0x1fa/0x410
 do_sys_openat2+0x121/0x1c0
 __x64_sys_openat+0x138/0x170
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f83d15169a4
Code: 24 20 48 8d 44 24 30 48 89 44 24 28 64 8b 04 25 18 00 00 00 85 c0 75 2c 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 76 60 48 8b 15 55 a4 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffffc98c4f0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffffc98c708 RCX: 00007f83d15169a4
RDX: 0000000000000000 RSI: 00007ffffc98df18 RDI: 00000000ffffff9c
RBP: 00007ffffc98df18 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffffc98c720 R14: 000056143ed96670 R15: 00007f83d1a9ca80
 </TASK>

Allocated by task 5987:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x230/0x3d0
 em28xx_v4l2_init+0x10b/0x2e70
 em28xx_init_extension+0x120/0x1c0
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30

Freed by task 5987:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5b/0x80
 kfree+0x18e/0x440
 em28xx_v4l2_init+0x1683/0x2e70
 em28xx_init_extension+0x120/0x1c0
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30

The buggy address belongs to the object at ffff888028490000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1856 bytes inside of
 freed 8192-byte region [ffff888028490000, ffff888028492000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x28490
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
ksm flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a442280 ffffea0000af2000 dead000000000003
raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a442280 ffffea0000af2000 dead000000000003
head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000a12401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5589, tgid 5589 (dhcpcd), ts 129114670426, free_ts 128735898321
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x370
 ___slab_alloc+0xbeb/0x1410
 __kmalloc_node_track_caller_noprof+0x2f8/0x4e0
 kmalloc_reserve+0x136/0x290
 __alloc_skb+0x142/0x2d0
 netlink_dump+0x167/0xe90
 netlink_recvmsg+0x676/0xa30
 sock_recvmsg+0x22c/0x270
 ____sys_recvmsg+0x1c9/0x460
 ___sys_recvmsg+0x1b5/0x510
 __x64_sys_recvmsg+0x198/0x260
 do_syscall_64+0xfa/0x3b0
page last free pid 793 tgid 793 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 sg_remove_scat+0x261/0x510
 sg_remove_sfp_usercontext+0x2b5/0x500
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30

Memory state around the buggy address:
 ffff888028490600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888028490680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888028490700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888028490780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888028490800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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